The ability to walk is important for independent living and when neurological or other injury affects this capacity, gait therapy is the traditional approach to re-train the nervous system. The approximately 5.8 million stroke survivors, and an additional 700,000 strokes occurring each year, many requiring gait therapy, illustrate the importance of this problem. In addition to stroke, many other neurological conditions and orthopedic injuries lead to significant gait impairment. Individuals with these conditions may be able to regain gait function through physical therapy.
Utilizing mechanical devices to deliver gait therapy is not a new idea and several devices have been developed for this purpose. The most common mechanical device is the treadmill. Treadmills reduce the amount of space required for therapy, in comparison to ground walking therapy, and encourage patients to maintain a constant gait velocity. While research indicates that treadmill gait therapy does not have a detrimental impact and improves training efficiency, and, in some cases, subjects who completed treadmill therapy regained more function compared to traditional physiotherapy techniques, treadmill therapy still requires a therapist to monitor pelvis movement and a second or third therapist to propel the leg or legs forward. Robotic rehabilitation devices for lower limb therapy have been built to attempt to automate the therapy process. Prior art robotic devices that have shown reliable outcomes include the Gait Trainer I (Reha-Stim)1, which is an end-effector based robot incorporating an adjustable body weight system and sliding foot plates secured to the patient's feet to impose a mechanically-fixed pattern of foot motion. Another prior art device includes the Lokomat (Hocoma)2, which includes a treadmill, an adjustable body weight support and imposes a fixed kinematic gait pattern determined from healthy subjects. These robotic devices do not reproduce the appropriate dynamic sensory input that occurs during normal gait and that is critical for gait rehabilitation. Neural inputs required to re-gain leg movement and balance include appropriate heel strike, toe-off, and swing phase during which gravity accelerates the foot towards the ground. However, prior art devices employing fixed foot motion or fixed kinematic gait patterns do not satisfy one or more of these neural inputs associated with normal gait. 1 Pohl M, Werner C, Holzgraefe, et al. Repetitive locomotor training and physiotherapy improve walking and basic activities of daily living after stoke: a single-blind, randomized mulicentre trial (Deutsche Ga. IngtrainerStudie, DEGAS.) Clinical Rehabilitation, 21: 17-27 (2007); Mehrholz, J, Werner C, Kugler J, Pohl M., Electromechanical-assisted training for walking after stroke (Review), The Cochrane Collaboration, Issue 4, (2007).2 Hidler J, Wisman W, Neckel N. Kinematic trajectories while walking within the Lokomat robotic gait-orthosis. Clinical Biomechanics. 23: 1251-1259 (2008); Jesernik S, Colombo G, Keller T, et al. Robotic orthosis Lokomat: a rehabilitation and research tool. Neuromodulation. 6: 108-115 (2003).
Thus, it is desirable to provide an interactive rehabilitation robotic device or apparatus for treadmill gait therapy that allows lower limb movement of a subject without the subject restricted to a fixed, rigid kinematic profile. In addition, it is desirable this robotic apparatus permit active participation of the subject and dynamic lower limb movement in response to the creation of a ground clearance that permits leg/foot swing and employs gravity to assist in forward leg/foot propulsion. It is desirable that the apparatus challenges a subject to increase his/her contribution to the leg/foot motion by monitoring the subject's performance and increasing treadmill speed as needed. It is also desirable that the apparatus further enable subject steps with an ecological heel strike. In this manner, the apparatus permits the subject to take advantage of natural gravitational, muscular and skeletal dynamics, while accomplishing toe-off, foot swing, and heel strike phases of a human gait, such that, the appropriate muscle groups of the subject receive the required neural input.